Multi-Technique Analysis of the Hydration in Three Different Copper Paddle-Wheel Metal-Organic Frameworks

The structural instability in humid environment of the majority of metal organic frameworks (MOFs) is a challenging obstacle for their industrial scale development. Recently, two extremely water-resistant MOFs have been synthetized, STAM-1 and STAM-17-OEt. Both STAM-1 and STAM-17-OEt contain copper paddle-wheels, like the well-known water sensitive HKUST-1, but different organic linkers. The crystal lattice of both STAM-1 and STAM-17-OEt undergo a phase transition upon interaction with water molecules. The unusual flexibility of STAM-1 and STAM-17-OEt allows the controlled breaking of some inter-paddle-wheel Cu-O interactions in the so-called “crumple zones”, with a mechanism called “hemilability” which is considered to have a crucial role for the stability of these MOFs towards water. In this work we present a detailed investigation on the different effects of water exposure on the local and long-range structures of HKUST-1, STAM-1 and STAM-17-OEt. In this work, Electron Paramagnetic Resonance (EPR) spec...